Field of the Invention
The present invention relates generally to catheters for performing medical procedures including percutaneous transluminal coronary angioplasty. More particularly, the present invention relates to balloon catheters with an improved proximal shaft design.
The use of intravascular catheters has become an effective method for treating many types of vascular disease. In general, an intravascular catheter is inserted into the vascular system of the patient and navigated through the vasculature to a desired target site. Using this method, virtually any target site in the patient""s vascular system may be accessed, including the coronary, cerebral, and peripheral vasculature. Examples of therapeutic purposes for intravascular catheters include percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA).
Intravascular catheters are commonly used in conjunction with a guidewire. A guidewire may be advanced through the patient""s vasculature until it has reached a target location. Once in place, a catheter may be threaded onto the guidewire and urged distally until the distal end of the catheter reaches a target location.
Intravascular catheters adapted for use with a guidewire typically are classified as over-the-wire (OTW) or single operator exchange (SOE). An OTW catheter includes a guidewire lumen extending from the distal tip of the catheter to the proximal end of the catheter. When intravascular catheters are used, it is common for physicians to remove one catheter and exchange it for another. While exchanging catheters, the guidewire should preferably be held in place so as to keep its distal end near the target area. A portion of the guidewire is typically grasped by the physician in order to withdraw the first catheter while maintaining the distal end of the guidewire in the desired position. To properly anchor the guidewire, a portion of the guidewire should preferably be exposed at all times so it is available for the physician to grasp. In the case of an OTW catheter, the length of the guidewire extending beyond the patient""s body should be longer than the catheter. Consequently, in many cases intravascular catheters are longer than 200 cm or require guidewire extensions to facilitate exchange, and there may be more than 200 cm of wire extending from the patient. Managing this length of wire during a catheter exchange procedure is awkward, and often requires more than one person. Additionally, contamination should be avoided by assuring that the guidewire is not dropped from the sterile field.
SOE catheters were developed in response to difficulties encountered when exchanging OTW catheters. Accordingly, SOE catheters have a relatively short guidewire lumen relative to the length of the catheter. Therefore, the length of guidewire extending beyond the body of the patient need only be slightly longer than the guidewire lumen of the catheter. The physician may anchor or hold the guidewire as the first catheter is removed from the body with the exchange occurring over the shorter guidewire lumen. The guidewire lumen of an SOE catheter typically includes a distal guidewire port disposed at the distal tip of the catheter and a proximal guidewire port disposed proximally of the distal end of the catheter.
When in use, intravascular catheters enter a patient""s vasculature at a convenient location and then are urged to a target region. Once the distal portion of the catheter has entered the patient""s vascular system, the physician may urge the distal tip forward by applying longitudinal forces to the proximal portion of the catheter. For the catheter to effectively communicate these longitudinal forces, it is desirable that the catheter have a high level of pushability and kink resistance particularly near the proximal end.
Frequently the path taken by a catheter through the vascular system is tortuous, requiring the catheter to change direction frequently. In some cases, it may even be necessary for the catheter to double back on itself. In order for the catheter to conform to a patient""s tortuous vascular system, it is desirable that intravascular catheters be very flexible, particularly near the distal end.
Further, while advancing the catheter through the tortuous path of the patients vasculature, physicians often apply torsional forces to the proximal portion of the catheter to aid in steering the catheter. Torsional forces applied on the proximal end must translate to the distal end to aid in steering. It is therefore desirable that the proximal portion of an intravascular catheter have a relatively high level of torquability to facilitate steering.
The need for this combination of performance features is often addressed by manufacturing a catheter that has two or more discrete tubular members having different performance characteristics. For example, a relatively flexible distal section may be connected to a relatively rigid proximal section. When a catheter is formed from two or more discrete tubular members, it is often necessary to form a bond between the distal end of one tubular member and the proximal end of another tubular member.
An approach used to enhance pushability and torquability of intravascular catheters is to construct the proximal end from hypodermic tubing, or a xe2x80x9chypotubexe2x80x9d. While a hypotube can add significant pushability and torquability to an intravascular catheter due to its intrinsic strength and rigidity, it can kink if bent too sharply.
A need, therefore, exists for the manufacturing of SOE intravascular catheters to include shaft designs that maintain pushability, flexibility, and torquability while limiting kinking.
The present invention relates generally to catheters for performing medical procedures including percutaneous transluminal coronary angioplasty. More particularly, the present invention relates to catheters with improved proximal shaft designs. A preferred embodiment of the current invention includes an elongate support member with a proximal and distal end. The distal end of the elongate support member can be connected to the proximal end of a mid-region, the distal end of the mid-region connected to a distal region of a catheter shaft. Preferably, the distal region of the catheter shaft includes a therapeutic element such as an angioplasty balloon.
Multiple materials can be used to manufacture the elongate support member in different embodiments of the current invention. For example, the elongate support member can be manufactured from materials including, but not limited to thermoplastics, high performance engineering resins, polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyurethane, polytetrafluoroethylene (PTFE), polyether-ether ketone (PEEK), polyimide, polyamide, polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysufone, nylon, perfluoro(propyl vinyl ether) (PFA), metals, stainless steel, nickel alloys, nickel-titanium alloys, or other alloys.
In the preferred embodiment of the current invention, the elongate support member is formed so as to define a plurality of flanges. Forming the elongate support member can be accomplished by multiple methods including, but not limited to rolling a metallic sheet, cutting hollow cylindrical stock, modifying hypodermic tubing, or extrusion. After forming the elongate support member, it may resemble shapes that can be, but are not limited to, generally hemi-cylindrical, generally semi-cylindrical, generally rounded, partially rounded, and combinations thereof.
The flanges of the elongate support member can be connected to each other by a multiplicity of means according to differing embodiments of the current invention. According to the preferred embodiment of the current invention, a linkage is used to connect the flanges. The linkage includes a multiplicity of forms including, but not limited to a sheath, asymmetric sheath, and polymer cap.
The linkage can be manufactured from a multiplicity of materials including, but not limited to, thermoplastics, high performance engineering resins, polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyurethane, polytetrafluoroethylene (PTFE), polyether-ether ketone (PEEK), polyimide, polyamide, polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysufone, nylon, and perfluoro(propyl vinyl ether) (PFA).
In a particular embodiment of the current invention, the linkage includes an asymmetric sheath. The sheath disposed about the elongate support member can be manufactured from materials including, but not limited to, polyether-ether ketone, polyimide, polyphenylene sulfide, and perfluoro(propyl vinyl ether). In differing embodiments of the current invention, in addition to a sheath, a linkage that directly connects the flanges may also be used. Further, combinations of different linkages may be used in multiple embodiments of the current invention. The sheath can be adhered to the elongate support member by a number of techniques including, but not limited to, heat shrinking.
Connection of the flanges defines a lumen extending from the proximal end of the catheter to the distal end of the elongate support member. The lumen may enable communication between the proximal and distal ends of the catheter. For example, the shaft may be used as an inflation lumen for angioplasty balloons. Additionally, the lumen of the formed elongate support member may be coated. For example, the elongate support member may be coated with polytetrafluoroethylene (PTFE).
In an exemplary embodiment of the current invention, the flanges are connected using an over wire extrusion method. According to this embodiment of the current invention, the linkage connecting the flanges is attached to the elongate support member by extrusion. For example, a wire is placed within an elongate support member comprising a plurality of flanges and extruded so as to attach a linkage disposed over the elongate support member. In an alternative embodiment of the current invention, the flanges are connected by adhesives. The adhesives include, but are not limited to, epoxy or polyurethane.
An additional embodiment of the current invention comprises the use of a polymer cap that is adhered with adhesive or thermal binding with a primer to connect the flanges. Preferably, the polymer cap is attached by first attaching a coupling agent or primer to the flanges. The coupling agent may allow easier attachment of the polymer cap to the flanges. Alternatively, the polymer cap may be attached to the flanges by thermal binding.